SPI clock pin configuration for nRF52840.

[Shivek]

Hi,

I am using nRF52840 on custom board. I am trying to configure SPI pins, but I am not getting anything on the clock pin. I can see the chip select pin going low and high which is good. But there is no clock on the pin. Following is the code snippet from my project.

#define MEM_CS                           NRF_GPIO_PIN_MAP(0,4)
#define MEM_SI                           NRF_GPIO_PIN_MAP(0,7)
#define MEM_SO                           NRF_GPIO_PIN_MAP(1,8)
#define MEM_SCK                          NRF_GPIO_PIN_MAP(0,13)

void memInit(void)
{
	    //GPIO configuration
        nrf_gpio_cfg_output(MEM_CS);
        nrf_gpio_cfg_output(MEM_SI);
        nrf_gpio_cfg_output(MEM_SCK);
        nrf_gpio_cfg_input(MEM_SO, GPIO_PIN_CNF_PULL_Pulldown);

                
        //SPI configuration
        nrf_drv_spi_config_t spi_config = NRF_DRV_SPI_DEFAULT_CONFIG;
        spi_config.ss_pin    = MEM_CS;
        spi_config.miso_pin  = MEM_SO;
        spi_config.mosi_pin  = MEM_SI;
        spi_config.sck_pin   = MEM_SCK;
        spi_config.bit_order = NRF_SPI_BIT_ORDER_MSB_FIRST;
        spi_config.frequency = NRF_SPI_FREQ_250K;
        spi_config.mode      = NRF_SPI_MODE_2;
        
        nrf_drv_spi_init(&spi, &spi_config, spi_event_handler, NULL);

}

uint32_t memId()
{
        __disable_irq();
        
        nrf_gpio_pin_clear(MEM_CS);         //Pin goes low now

        err  = nrf_drv_spi_transfer(&spi, p_tx_buffer, sizeof(tx_buffer), NULL, 0);  
        nrf_delay_ms(100);
        
        nrf_gpio_pin_set(MEM_CS);           //Pin goes high now

	    __enable_irq();
        return err;
}

For my custom board configuration I have set Preprocessor definitions to BOARD_CUSTOM. But for simplicity, I have defined the pins in the source code file. I am thinking to test it first and then I can define the pins for SPI in custom_board.h. On the custom board I have checked for the pins they are not connected to any other peripheral. 

For development, I am using SES with nRF SDK15.0.0 and Softdevice S140. 

Any insight would be appreciated.

Thanks!

[Shivek]

Hi Einar,

Einar Thorsrud said:

So you should at least remove the call to __disable_irq().

I tried removing the line __disable_irq(). But it didn't help. I am still not able to see the clock on the pin. I tried the code with the board supplied by Fanstel. I have attached the document from them which has the schematic for the dev kit I am using. I will really appreciate if you can have a look on the document and let me know if there is anything I am doing wrong with the pin selection for the purpose.

M2_LN60E40F+Product+Specifications.pdf

The LN60E40F is a module based on nRF9160 and nRF52840. For the schematic you can go to the page no. 25 of this document. The schematic is not having good resolution and that is frustrating for me as well. 

Thank you for your efforts.

Regards,

Shivek

[hmolesworth]

Confusing schematic, but it looks like nRF52840 P0.13 is not available on a pin; P013 may instead be the P0.13 pin on the nRF9160.  Edit: oh, maybe it's the other way round which means it is available. Hmm ..

[Einar Thorsrud]

Good points. Shivek: Perhaps it is worth configuring the SCK and other pins as normal GPIOs that you toggle, and check with a logic analyzer to verify that the pin mapping is actually what you think it is?

[Shivek]

Hi Hmolesworth,

Thanks for your time to give it a look. I have tried using P0.13 from nRF52840 as normal GPIO, and I was able to control the state of the pin, i.e., toggle the pin after some time. So, that's why I am sure about pin P0.13 and on top of that I tested with multimeter there is a connection from M2 connector pin(the pin which is connected to nRF52840 P0.13 pin on the LN60E840E module) to the connector header on the dev kit. 

Regards,

Shivek

[Shivek]

Hi Einar, 

As I mentioned in my response to hmolesworth, I have tried using P0.13 as normal GPIO and tested toggling the pin, I was able to see the pin toggling on scope. But if I am using the same pin for SPI clock, it won't get any clock going on that pin.

Would you be able to send a simple example(other than which is included in SDK), which I can test on my hardware just by simply changing the pins?

 I think that would make me clear that whether its a hardware issue or software issue.

Regards,

Shivek

[hmolesworth]

I am not getting anything on the clock pin -- at 250kHz clock I would think even a cheap 'scope would see that, but are you using (say) some low-cost analyser which might have too low a resolution?

p_tx_buffer,and sizeof(tx_buffer) are inconsistent (different buffers), maybe make the buffer size bigger so easier to see the clocks. Hopefully the buffer is not defined const ..